The present invention generally relates to a coastal structure and a method of its placement. More particularly, the present invention relates to a middle armor block for a coastal structure and a method of placement of its block with a hydraulic stability of a slope surface and an economical construction cost.
Generally, the coastal structure, which is located inside harbor or leeward, is installed underwater for protecting facility structures from transportation of wave energy. When the coastal structure is constructed for a breakwater or seawall, a sandy rock is used at an under layer of the coastal structure for hydraulically stabilizing on the slope surface, and artificial armor units are used at an upper layer of the coastal structure, such as a tetrapod, a dolos, an accropode or a core-loc for dissipating wave energy. Specifically, for a design method of the breakwater, a rubble mound breaker is widely adopted to install the artificial armor units for the front slope surface. Recently, Caisson adopted a composite type structure for constructing the breakwater.
Due to the increasing amount of trades and the size of surface freighters, there is a tendency to construct the breakwater on the deeper water advanced from the coast. Therefore, the weight of coating materials is expected to increase for protecting the structure against bigger waves. For the design of newly developing harbors, the severer weather and the bigger waves should be considered in comparison to the design conditions of a conventional harbor.
For protecting the important facilities on the leeward, the breakwater or seawall should be designed with at least a 100 year return period.
According to the conventional standard design method for a section, in case of constructing a large sized harbor, or a conventional rubble mound breakwater and the seawall, a weight ratio of an upper layer of coating materials and a lower layer of sandy stones would be 1:1/10. (Coastal Engineering Research Center, U.S. Army Corps of Engineers, 1984, Shore Protection Manual Pg. 7-228). It is possible to provide a demanded weight of the coating materials because the coating materials could be possibly manufactured by an artificial casting. But, it is not easy to provide enough amount of corresponding weight of the under layer of sandy stones because the natural rocks for under layer of sandy stones are usually provided nearby the construction site.
To solve the problems described above, a conventional artificial armor block or a slightly modified type of block is used instead of the lower layer of sandy rocks for the front slope layer coated block. In this case, it would not clearly be stable for the hydraulic characteristics of the whole section if the lower layer were exposed during a construction or placed together with the front slope layer coated block.
On the other hand, the Grovel sea level is raised because of the Laninor phenomenon. As a result, it may not be occurred the expected dissipation of wave energy due to wave breaking in the shallow water zone. However, the current design for the coastal structure does not consider the raised sea level.
An object of this invention is to overcome the problems described above and provide an artificial block (hereinafter xe2x80x9chalf-locxe2x80x9d to replace the sandy stones.
Another object of this invention is to provide a new form of the middle armor block for improving the ability of construction at the construction site and the stability of the breakwater.
Another object of this invention is to provide a safety placement method when a middle armor block is constructed along with the front slope layer coating material.
In order to accomplish the above objectives of this invention, the new form of the middle armor block comprises a body having a shape of octagon column with a rectangle side and a perforated hole at the center of the top of the body.
Four legs are integrally formed at each of a lower portion of the legs and each corner of the legs and the foot is chamfered.
The other objects and features of this invention will be in part apparent and in part pointed out hereinafter.